Filp-chip sub-assembly, methods of making same and device including same

ABSTRACT

An electronic device including a multi-chip die and a substrate member, said multi-chip die includes a plurality of integrated circuit chips which are integrally formed on the multi-chip die as a unitary member, each the integrated chip includes a plurality of electrodes for making external electrical contacts, the substrate member includes a circuit of a pre-determined pattern and a plurality of electric contacts disposed for making corresponding electrical connections with the electrodes of the integrated chips of the multi-chip die, the plurality of integrated circuit chips of the multi-chip die being connected as a unitary member to the substrate member.

FIELD OF THE INVENTION

This invention relates to electronic modules, devices, sub-assembliesand methods for making same. More particularly, this invention relatesto electronic modules, devices and sub-assemblies with an LCD displayand methods for making same. More specifically, although of course notsolely limiting thereto, this invention relates to electronic devices,modules and sub-assemblies containing an LCD display element withflip-chip bonded semiconductor integrated circuits.

BACKGROUND OF THE INVENTION

The use of semiconductor integrated circuits, especially in electronicdevices, have greatly proliferated since their invention in early1960's. Traditionally, semiconductor integrated circuits are providedand used in packaged forms with a semiconductor chip bonded to alead-frame header or other package or substrate by find gold or aluminumwires that loop from contact pads disposed around the periphery of thecircuitry surface of the semiconductor chips.

In order to alleviate the adverse parasitic effects as well asfulfilling the industry-wide demand for high lead counts and small footprints, the “flip-chip” method or technology for bonding a semiconductorintegrated circuit chip to a substrate was introduced. The flip-chipbonding technology has been described in many publications such as, forexample, U.S. Pat. No. 3,429,040 issued to L. F. Miller in 1969 and manyother subsequently published US patent specifications. The conventionalway to bond a semiconductor integrated circuit chip onto a substrate isby firstly flipping the semiconductor chip over so that the contact padsdisposed on the top peripheral surface of the semiconductor chip isdirectly opposite the surface of a substrate member on which there areformed a corresponding set of contact pads for making interconnectionsbetween the semiconductor chip and the substrate member. Thecorresponding contact pads on the integrated circuit chip and thesubstrate member are then aligned and subsequently connected together tocomplete the electrical connection. Typically, the external electrodesor contact pads on an integrated circuit chip are provided with solderballs or bumps to ensure reliable connection and the components areconnected by appropriate connection methods or means such as, forexample, reflow soldering.

However, with the ever increasing demand for additional and improvedperformance from electric devices, more and more integrated circuits arerequired on an electronic device and the cost-effectiveness or benefitsof the conventional flip-chip bonding technology begin to decline.

For example, in the early versions of mobile telephones or hand-heldgames, a single integrated circuit display driver chip may be sufficientto drive the entire display screen. However, to fulfill the everincreasing demand for additional features to be available for displayand the ever increasing demand for higher resolution of such displayfeatures, a plurality of integrated circuit display drivers may berequired for a single display means which is typically, but not limitedto, an LCD display screen.

Likewise, with the ever increasing demand for further miniaturization ofhand-held electronic devices such as, for example, mobile phones orhand-held computers, coupled with the ever increasing operating speed orfrequencies of such devices, it is a clear trend that more and moreintegrated circuit chips connected by non-wire bonding means will berequired by such electronic devices. On the other hand, it is noted thatthe yielding rate or productivity of electronic devices, modules orsub-assemblies declines significantly with the increasing number of“flip-chip” bonded integrated circuit chips. Hence, it will be highlydesirable if there can be provided electronic devices, modules orsub-assemblies containing a plurality of integrated circuitry chipsconnected by the non-wire bonding means while alleviating the adverseconsequences associated with the conventional flip-chip bondingtechnologies or methods. Similarly, it will be highly desirable if therecan be made available electronic devices, modules including a pluralityof integrated circuit chips connected by non-bonding wire means whilealleviating the known adverse consequences of conventional flip-chiptechnology and method.

OBJECT OF THE INVENTION

Accordingly, it is an object of the present invention to provideelectronic devices, modules and sub-assemblies including a plurality ofsemiconductor integrated circuit chips connected by non-bonding wireconnection means. Likewise, it is also an object of the presentinvention to provide methods for assembling electronic sub-assemblies,modules and devices including a plurality of semiconductor integratedcircuit chips connected by non-wire bonding connection means, therebyenjoying the characteristic benefits afforded by the flip-chip bondingmethod while alleviating the adverse consequences or shortcomings ofconventional flip-chip technologies.

More specifically, although of course not solely limiting thereto, it isalso an object of the present invention to provide LCD display modules,sub-assemblies or electronic devices incorporating same with a pluralityof semiconductor integrated circuit chips connected by non-wire bondingmeans to fulfill the demand for ever increasing degree of complexity ofthe display features and/or higher resolution to be expected by theconsumers or the general public. At a minimum, it is an object of thepresent invention to provide the public with a useful choice ofelectronic modules, sub-assemblies, electronic devices incorporatingsame and method for making same.

SUMMARY OF THE INVENTION

Accordingly, it is a first aspect of the present invention to provide anelectronic device including a multi-chip die and a substrate member,said multi-chip die includes a plurality of integrated circuit chipswhich are integrally formed on said multi-chip die as a unitary member,each said integrated chip includes a plurality of electrodes for makingexternal electrical contacts, said substrate member includes a circuitof a pre-determined pattern and a plurality of electric contactsdisposed for making corresponding electrical connections with theelectrodes of said integrated chips of said multi-chip die, saidplurality of integrated circuit chips of said multi-chip die beingconnected as a unitary member to said substrate member.

According to a second aspect of the present invention, there is providedan electronic module or sub-assembly including a multi-chip die and asubstrate member, said multi-chip die includes a plurality of integratedcircuit chips which are integrally formed on said multi-chip die as aunitary member, each said integrated chip includes a plurality ofelectrodes for making external electrical contacts, said substratemember includes a circuit of a pre-determined pattern and a plurality ofelectric contacts disposed for making corresponding electricalconnections with the electrodes of said integrated chips of saidmulti-chip die, said plurality of integrated circuit chips of saidmulti-chip die being connected as a unitary member to said substratemember.

According to a third aspect of the present invention, there is provideda method of connecting a plurality of integrated circuit chips to asubstrate member, wherein said substrate member includes apre-determined circuit pattern with a plurality of contact pads, saidmethod includes:

-   -   selecting a plurality of integrated circuit chips from a        processed semi conductor wafer,    -   removing said plurality of integrated circuit chips from said        wafer as an unitary member,    -   aligning the electrodes on said plurality of integrated circuit        chips corresponding with said plurality of contact pads on said        substrate member,    -   electrically connecting said electrodes with said contact pads.

Preferably, said plurality of integrated circuits on said multi-chip diebeing electrically isolated from each other before removal from thesemiconductor wafer on which said integrated circuit chips are formed.

Preferably, said multi-chip die and said substrate member beingconnected by a flip-chip method.

Preferably, an anisotropic conductive film layer is disposed betweensaid multi-chip die and said substrate member for making electricalconnection between the electrodes on said multi-chip die and thecontacts on said substrate.

Preferably, said substrate member being a glass substrate with at leasta printed circuit.

Preferably, said electronic device includes a liquid crystal display(LCD) means.

Preferably, said liquid crystal display (LCD) being mounted on saidsubstrate member.

Preferably, said substrate member includes a LCD glass substrate.

Preferably, said integrated chips include logic and memory elements.

Preferably, said pattern includes Indium Tin Oxide (ITO) wireconnection.

Preferably, an anisotropic conductive film layer is disposed betweensaid multi-chip die and said substrate member for making electricalconnection between the electrodes on said multi-chip die and thecontacts on said substrate, said electronic device includes a liquidcrystal display means.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be explained infurther detail below by way of examples and with reference to theaccompanying drawings, in which:

FIG. 1 shows schematically a processed semiconductor wafer including anarray of electrically isolated integrated circuit chips,

FIG. 2 illustrates an LCD display module or sub-assembly indicating thecorrelation between the electrodes on a plurality of integrated circuitchips on a multi-chip die and the corresponding contact pads disposed ona substrate member,

FIG. 3 illustrates schematically the module or sub-assembly of FIG. 2when the multi-chip die has been duly aligned with the contact pads onthe substrate member and connected,

FIG. 4 is a cross-sectional elevated view showing electrical connectionbetween the multi-chip die and the substrate made according to a firstpreferred method of the present invention,

FIG. 5 illustrates a display module or sub-assembly including amulti-chip die integrally formed with three integrated circuit chipsmounted on the module according to the methods of the present invention,

FIG. 6 illustrates a display means, module or sub-assembly including twomulti-chip dies with two integrated circuit chips on each die andconnected to the electronic means, module or sub-assembly according tothe methods of the present invention,

FIG. 7 illustrates a second embodiment of the methods for fulfilling thepresent invention and showing a multi-chip die in a substrate memberbefore connection,

FIG. 8 illustrates a second embodiment of the methods for fulfilling thepresent invention and showing the multi-chip die in a substrate memberafter electrical connection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring firstly to FIG. 1, there is shown a processed semiconductorwafer 10 containing a plurality of integrated chip 11. Typically, theintegrated circuit chips 11 are integrally formed on the same wafer andare normally isolated or not interconnected electrically while still onthe wafer. Usually, the integrated circuit chips are arranged in orderlyarray with constant separation distances between adjacent integratedcircuit (IC) chips. Furthermore, while a single type of IC is usuallyfound on a single processed wafer, it is not unusual that differenttypes of isolated ICs are formed on the same wafer. In the presentexample, although each of the integrated circuit chip is designated withthe numeral 11 for convenience, the ICs may be different or identicalwithout loss of generality since the reference to individual ICs isprimarily for illustrating the electrical connection between the ICs 11and the corresponding substrate member 22. Of course, each of the ICs isformed with contact pads or electrodes for making electrical connectionswith external circuitry or other components of the same module ordevice. Of course, the integrated circuits may contain active as well aspassive elements according largely to the purposes of application.

To prepare for the present invention, the IC chips 11 on the processedwafer are divided into groups each of which generally include aplurality of ICs. For example, the processed wafer 10 may be dividedinto groups comprising two, three, four or more ICs. Of course, theremay be portions of the wafer which is not formed with an IC or a groupmay only comprise a single IC, depending on the wafer.

Turning now to FIG. 2, there is shown a semi-finished liquid crystaldisplay (LCD) display module 20 with an LCD display means 21 alreadymounted an electrically connected to a substrate member 22 with acircuit of a pre-determined conductive pattern 23. For an LCD displaymodule, an LCD glass substrate is commonly used, although other types ofsubstrates can of course be used. The conductive pattern or circuits areusually printed made or developed on the top surface of the substratemember 22, although other appropriate methods for forming definitiveconductive patterns, tracks or circuits can equally be applied.

In order to alleviate the shortcomings associated with the conventional“flip-chip” bonding technology, a multi-chip die containing a pluralityof ICs integrally formed on the same multi-chip die are bonded as aunitary member, i.e. as a single piece containing two individual ICs, tothe substrate member. The individual ICs are usually not interconnectedwhile on the multi-chip die, although it should be understood thatcertain interconnections, for example, input/output connection, supplyrails, etc. may be pre-formed between the individual ICs for furtherbenefits. In order to form electrical connections between the ICs on themulti-chip die 12 and the conductive pattern or circuit 23 on thesubstrate, a plurality of conductive pads 24 are formed on theconductive pattern or circuit spatially corresponding to the counterpartelectrodes on the ICs 11 of the multi-chip die 12. In general, theconductive pads 24 formed on the substrate 22 are generally disposedwith relative spacing and distance similar to that between theelectrodes of the ICs 11 on the multi-chip die 12.

For the sake of completeness, it will be noted that the electrodes 14 ofthe ICs 11 are disposed on the side of the multi-chip die 12 directlyopposite the top surface of the conductive pattern bearing top surfaceof the substrate member 22.

It would be observed from FIG. 3, in which a complete module includingthe LCD display member 21 and the multi-chip die have been dulyconnected, that the electrodes on the ICs 11 of the multi-chip 12generally overlap or overlay the corresponding conductive pads 24 on thesubstrate member 22. A variation of an LCD display module orsub-assembly constructed according to the present invention is shown inFIG. 5 in which a multi-chip die 12 comprising three integrated circuitchips 11 are mounted or bonded to the substrate member 22 as a unitarymember and according to the methods of the present invention. Adifferent display pattern is shown here to illustrate the increasedcomplexity of the features to be displayed. Similarly, an LCD displayconstructed according to the methods of the present invention with twomulti-chip dies each containing two ICs on the same die and individuallymounted onto the substrate member 22 of the module are shown toillustrate the flexibility and sophistication of the assembling methodof the present invention and the resulting modules or devices.

In the present specification, it will be understood same numerals willbe used to designate parts of the same general characteristics for thesake of brevity unless the context otherwise requires.

Turning now to the making or assembly of the module, sub-assembly ordevice containing the present invention, a multi-chip die comprising aplurality of IC chips, for example, two, three, four or more areremoved, for example, by die sawing from the processed wafer 10 toobtain the desirable multi-chip die 12. Thus, a plurality of ICs whichare physically attached and preferably electrically isolated areobtained after die sawing. To provide easy electrical connection to theIC chip, conductive bumps or balls are applied to the electrodes orcontact pads on the ICs 11. The contact pads or electrodes 14 on the ICare generally exposed for electrical connection and are generallydisposed around the top peripheral surface of an IC chip. The conductivebumps on the IC may contain, for example, gold, indium, copper, such ascopper UBM, copper post, lead/tin solder, Nickel, lead-free pure-tin,lead-free-tin bismuth, lead-free tin-silver or other appropriate bumpingmaterials. The multi-chip die is then flipped over so that the surfaceof the multi-chip die, i.e. the surface of the wafer with the contactelectrodes 14 exposed, is opposite to the top surface of the substratemember 22 on which a pattern of conductive pads have already beenformed.

In particular, the pattern of conductive pads or preferably printedcircuits are also provided with conductive pads arranged in spatialcorrelation to the electrodes 14 on the ICs so that the contactelectrodes or pads of the ICs on the flipped multi-chip die will overlapor overlay the conductive pads 24 already formed or printed on the topsurface of the substrate member 22 when the multi-chip die are properlyaligned with the conductive pattern on the substrate member 22. Afterthe multi-chip die and the substrate member have been duly aligned, amore permanent electrical connection process will then take place.

As a general note, materials suitable for use as the substrate member 22may include Liquid Crystal Display (LCD) glass, Printed wiring board(PWB), Tape Carrier package (TCP), Ball Grid Array (BGA), semiconductorchip, plastic, ceramic, flexible film, etc.

Examples illustrating the electrical connection between the multi-chipdie 12 and the substrate member 22 will be illustrated in more detailbelow.

EXAMPLE 1 Connection with an Anisotropic Conductive Film “ACF”

Referring to FIG. 4, there is shown in elevation generally along theline A-A of FIG. 3 in more detail the electrical connection between theICs 11 on the multi-chip die 12 with the substrate member 22. In thispresent mode of connection, an ACF film is placed between the flippedtop surface of the multi-chip 12 and the conductive pads 24 carryingsurface of the substrate before the multi-chip die 12 is placed withproper spatial alignment with the conductive pads 24 on the substratemember. The ACF is interposed in the space separating the ICs 11 and thesubstrate member 22 as an underfill.

In general, ACF is made of thermosetting resin, such as epoxy resin, orof thermoplastic resin, such as polyethylene, with electrode conductiveparticles dispersed in the resin. When the ACF is interposed between theconductive bumps 15 of the ICs and the conductive pads 24 of thesubstrate member 22, electrical connection is obtained between theconductive bumps 15 of the IC chips 11 and the conductive pads 24 of thesubstrate member 22. The IC chips 11 will be held in position by theresin of the ACF and will be more permanently fixed after curing becauseof the nature of the thermosetting or thermoplastic materials. Thus, theICs may be reliably mounted and connected to perform the necessaryfunctions.

Examples of known ACF which may be used in the present application areas follows:

-   (1) FC 262 B produced by Hitachi Chemical Co., Ltd. (epoxy type    resin containing Ni particles)-   (2) MJ 932 and MJ 353 produced by Sony Chemicals Corporation (epoxy    type resin containing acrylic resin particles plated with Ni or Au).

EXAMPLE 2 Connection by Reflow Soldering Process

Referring to FIGS. 7 and 8, a second mode of connection between the ICs11 on the multi-chip die 12 will be explained in more detail.

Similar to the example above, the electrodes or conductive pads 14 onthe ICs 11 of the multi-chip die are provided with conductive bumps 15to ensure proper and reliable electrical connections. Similar to theprocess above, an underfill layer 104 is provided on the top surface ofthe substrate member. Masking 105 is provided at appropriate locationsto prevent interferences or short circuits due to overflow of thebumping when melted. The appropriate underfill for the present processincludes, for example, no-flow or compressive underfill such as epoxybased liquid. After the ICs 11 on the multi-chip die 12 have beenproperly aligned and mounted on the substrate member, the semi-assembledmodule is then subject to reflow soldering to impart more permanentelectrical connections between the two components.

Thus, by way of the present invention, a plurality of integrated chipscan be mounted on a substrate member utilizing a process which is akinto the one-chip flip-chip mounting technology while alleviating themajor shortcomings of conventional flip-chip technologies. In thispresent methods and invention, the need to sequentially mount and aligna plurality of ICs with many different steps, thereby jeopardizing theproductivity or cost benefits of flip-chip technologies, is alleviated.In this regard, it will be noted that by employing a plurality or amultiplicity of identical or non-identical ICs on the same multi-chipdie, the complexity of the features that can be produced on an LCDdisplay module illustrated in the present invention can be expandedwithout undue introducing complexity in the assembling process.

While the present invention has been explained by reference to thepreferred embodiments described above, it will be appreciated that theembodiments are only examples provided to illustrate the presentinvention and are not meant to be restrictive on the scope of thepresent invention. This invention should be determined from the generalprinciples and spirit of the invention as described above. Inparticular, variations or modifications which are obvious or trivial topersons skilled in the art, as well as improvements made on the basis ofthe present invention, should be considered as falling within the scopeand boundary of the present invention. Furthermore, while the presentinvention has been explained by reference to a module with an LCDdisplay means, it should be appreciated that the invention can apply,whether with or without modification, to other electronic devices,sub-assemblies device and apparatus without loss of generality.

1. An electronic device including a multi-chip die and a substratemember, said multi-chip die includes a plurality of integrated circuitchips which are integrally formed on said multi-chip die as a unitarymember, each said integrated chip includes a plurality of electrodes formaking external electrical contacts, said substrate member includes acircuit of a pre-determined pattern and a plurality of electric contactsdisposed for making corresponding electrical connections with theelectrodes of said integrated chips of said multi-chip die, saidplurality of integrated circuit chips of said multi-chip die beingconnected as a unitary member to said substrate member.
 2. An electronicdevice according to claim 1, wherein said plurality of integratedcircuits on said multi-chip die being electrically isolated from eachother before removal from the semiconductor wafer on which saidintegrated circuit chips are formed.
 3. An electronic device accordingto claim 1, wherein said multi-chip die and said substrate member beingconnected by a flip-chip method.
 4. An electronic device according toclaim 3, wherein an anisotropic conductive film layer is disposedbetween said multi-chip die and said substrate member for makingelectrical connection between the electrodes on said multi-chip die andthe contacts on said substrate.
 5. An electronic device according toclaim 1, wherein said substrate member being a glass substrate with atleast a printed circuit.
 6. An electronic device according to claim 1,wherein said electronic device includes a liquid crystal display (LCD)means.
 7. An electronic device according to claim 6, wherein said liquidcrystal display (LCD) being mounted on said substrate member.
 8. Anelectronic device according to claim 7, wherein said substrate memberincludes a LCD glass substrate.
 9. An electronic device according toclaim 7, wherein said integrated chips include logic and memoryelements.
 10. An electronic device according to claim 1, wherein saidpattern includes Indium Tin Oxide (ITO) wire connection.
 11. Anelectronic sub-assembly including a multi-chip die and a substratemember, said multi-chip die includes a plurality of integrated circuitchips which are integrally formed on said multi-chip die as a unitarymember, each said integrated chip includes a plurality of electrodes formaking external electrical contacts, said substrate member includes acircuit of a pre-determined pattern and a plurality of electric contactsdisposed for making corresponding electrical connections with theelectrodes of said integrated chips of said multi-chip die, saidplurality of integrated circuit chips of said multi-chip die beingconnected as a unitary member to said substrate member.
 12. A method ofconnecting a plurality of integrated circuit chips to a substratemember, wherein said substrate member includes a pre-determined circuitpattern with a plurality of contact pads, said method includes:selecting a plurality of integrated circuit chips from a processedsemi-conductor wafer, removing said plurality of integrated circuitchips from said wafer as an unitary member, aligning the electrodes onsaid plurality of integrated circuit chips corresponding with saidplurality of contact pads on said substrate member, electricallyconnecting said electrodes with said contact pads.
 13. An electronicdevice including a plurality of semiconductor integrated circuitsconnected according to the method of claim 12, characterised in thatsaid plurality of integrated circuits are integrally formed on the samesemiconductor wafer.
 14. An electronic device according to claim 13,characterized in that said plurality of integrated circuits on the samesemiconductor wafer are not interconnected by means on saidsemiconductor wafer.
 15. An electronic device according to claim 13,characterized in that said multi-chip die and said substrate memberbeing connected by a flip-chip method.
 16. An electronic deviceaccording to claim 13, characterized in that an anisotropic conductivefilm layer is disposed between said multi-chip die and said substratemember for making electrical connection between the electrodes on saidmulti-chip die and the contacts on said substrate.
 17. An electronicdevice according to claim 13, characterized in that an anisotropicconductive film layer is disposed between said multi-chip die and saidsubstrate member for making electrical connection between the electrodeson said multi-chip die and the contacts on said substrate, saidelectronic device includes a liquid crystal display means.